HP HP-21 - Manual Storage Register; Storing and Recallingdata

Press Display
3 [2) 5410.67
=
[x] Cubic feet that Daedalus has
increased the balloon’s
volume.
Manual Storage Register
In addition to the four automatic memories of the stack regis-
ters, the HP-21 also has a storage register that is manually
operated, and unaffected by operations within the stack. Keys
used to manipulate the manual storage register are By, A,
], L], [, [w].
Storing and Recalling Data
To store a number appearing in the display (whether the result
of a calculation or a keystroke entry), merely press B . If
the storage register already has a number in it, the old number
will be overwritten by the new one. The value in the displayed
X-register will remain unchanged.
To recall a number from the manual storage register, press the
key. Recalling a number does not remove it from the
storage register, but only copies the stored number into the
displayed X-register. Recalling a number will cause the stack
to lift (unless follows a [Z%3 or an ).
The original number will remain in the storage register until
either:
1. A new number is placed in the storage register over the
old one.
2. The calculator is turned off.
To clear only the manual storage register, press 0 BY.
Example: A customer at Hepzibah Pyncheon’s Emporium
has bought three items priced at $1000, $2000, and $3000,
respectively. Hepzibah’s policy is to grant a 5% discount on
all purchases over $500. How much will the customer pay for
each of the three items? What is the total cost?